1. Field of the Disclosure
This disclosure generally relates to a touch sensor and, more particularly, to a single-layer capacitive touch sensor with reduced dead zones.
2. Description of the Related Art
The conventional touch sensor, for example a resistive touch sensor generally includes a two-layer structure (e.g. thin film electrodes) and a steady voltage is applied thereto. Spacers are inserted between the two layers to isolate the two layers from each other. When a user applies a pressure through a finger or a touch pen to a position on the two-layer structure, the two-layer structure is electrically conducted (i.e. short) at the position. Therefore, a control IC may calculate the position contacted by the user according to voltage variations of an electrically conducted position and transfer into a position signal to be sent to a host so as to accomplish a corresponding action or perform a predetermined command.
However, since the sensing mechanism of the resistive touch sensor is implemented by mechanical pressing, in order to improve the durability of the product, the soft material (e.g. PET films) of the resistive touch sensor for being pressed by the user should have characteristics of pressure resistant, anti-deformation, and wear resistant. Nevertheless, the light transmittance of the resistive touch sensor can degrade with the accumulation of usage time and frequencies of the product. Especially the abrasion is caused at specific areas such as frequent touched positions thereby reducing the conductivity of the thin film electrodes. In addition, in order to compensate for the disadvantage due to the low-transmittance material, a stronger backlight will be applied such that the power consumption of the whole device is increased as well.
Another capacitive touch sensor generates a mutual capacitance through the contact between a plurality of thin film electrodes and a finger of a user or a conductive object, and then detects capacitance variations thereof through a control IC to accordingly calculate contact positions. Compared with the resistive touch sensor, when the capacitive touch sensor is used, the user only needs to slightly touch rather than press with a fingertip such that the problem of sensitivity reducing due to the abrasion will not be generated. Therefore, the life time of the device can be extended. However, the conventional capacitive touch sensor is designed with at least 3 layers (e.g. an x-axis sensing layer, a y-axis sensing layer and a shielding layer) and more complex control ICs thereby having problems of reduced transmittance, increased thickness and high cost.
For simplifying the manufacturing process, the industry further provides a capacitive touch sensor technology having a single-layer structure to overcome the described disadvantages. However, with the increasing of the size and resolution of the touch device, the single-layer structure has a large number of sensing units and traces electrically connected to the sensing units. FIG. 1 is a schematic diagram of a conventional single-layer capacitive touch sensor. The single-layer capacitive touch sensor 9 includes a plurality of sensing units 90 arranged in a matrix on a substrate 92, wherein each sensing unit 90 is composed of a sensing electrode ES and a driving electrode ED and electrically connected to a trace 905. Then, the traces 905 are electrically connected to a control IC along a direction (e.g. the bottom of the substrate 92 as shown in FIG. 1). In the conventional design, the pattern design of every sensing unit 90 is the same to allow the predetermined capacitance of the sensing units to be the same in a passive way. Therefore, the trace area outside the sensing electrode ES and the driving electrode ED cannot be utilized efficiently to have the problem of dead zones being formed in the areas with traces. The dead zones may cause a plurality of sensing discontinuities of the touch sensor.